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The greenhouse gases methane (CH4) and carbon dioxide (CO2) are end products of microbial anaerobic degradation of organic matter (OM) in lake sediments. Although previous research has shown that phytoplankton lipid content influences sediment methanogenesis, current understanding on how OM quality affects methanogenesis is still limited. Such information is needed to more accurately assess how lake greenhouse gas emissions may change in response to anthropogenic activities. We cultured 11 phytoplankton species from five classes and studied how taxonomic identity, C : N ratio, lipid content, and fatty acid composition of phytoplankton biomass affects the CH4 and net CO2 production in anaerobic lake sediments with an incubation experiment that lasted > 100 d. The carbon‐normalized potential CH4 (0.09–0.23 μmol mg C−1 d−1) and net CO2 (0.09–0.28 μmol mg C−1 d−1) production rates were not related to phytoplankton taxonomic affiliation (e.g., class, species), C : N ratio, or fatty acid composition of algal biomass. Methane or net CO2 production potentials did not increase with higher lipid content (10–30%); however, total fatty acid content had a weak correlation with CH4 production potential. In contrast to previous research, our results suggest that lipid content is of minor importance in determining methanogenesis rates from the biomass of multispecies phytoplankton communities settling on sediments. The decrease in CO2 concentration and the correlation between stable carbon isotope signatures of CH4 and molar ratio of CH4 and CO2 at the end of the experiment may indicate that importance of hydrogenotrophic methanogenesis, which uses CO2 when other substrates become limiting, increased during the long incubation. [ABSTRACT FROM AUTHOR]

The booming progress of biomass fuels in the enhancement of energy sustainability has been witnessed over the past few decades. Drying or moisture content reduction is a critical pretreatment step for the efficient utilization of wet biomass fuels whose improvement requires this study to focus on the effect of the transportation behavior of biomass fuels inside drying facilities. Experiments were performed under a variety of operating conditions in order to determine the residence time distribution (RTD) and flow characteristics of s‐liked biomass fuels in the process of transportation. A series of experiments are carried out in a rotary drum with different baffle structures, a length of 1850 mm and a diameter of 770 mm. Meanwhile, s‐liked and CO2 expanded biomass particles were taken as standard and tracer materials. RTD and scattering and fallout angles are measured and studied under the conditions of different baffle heights (64‐184 mm), numbers (2‐8), installation slopes (70°‐110°), rectangular bend heights (24.8‐62.5 mm), and bend slopes (90°‐150°). The Taylor model can appropriately estimate the mean residence time (MRT) of particles in a rotating drum with variety of baffle structures, such as baffle height, number, and bend slope. [ABSTRACT FROM AUTHOR]

While inundated, small ponds (< 1000 m2 area) account for disproportionately large contributions of CO2 efflux to the global carbon budget and also store carbon in anoxic sediments. However, pond hydrology is shifting toward increasingly dry conditions in alpine and temperate zones, which might lead to increased exposure of shallow pond sediments. We analyzed sediment CO2 efflux rates in dried sediments of multiple ponds of varying hydrology and sediment characteristics at montane and subalpine elevations near the Rocky Mountain Biological Laboratory in Colorado. Average CO2 efflux rates from exposed sediments, 331.5 ± 11.5 mmol m−2 d−1 at the montane sites and 142.8 ± 45.1 mmol m−2 d−1 at the subalpine sites, were 10 times higher than average CO2 efflux rates from pond water. Principal components analysis to reduce dimensionality of sediment characteristics revealed that random inter‐pond differences rather than exposure timing or hydroperiod drove variation among sediments. In linear mixed effects models of CO2 flux rates, significant predictors included sediment moisture and temperature, pH, total organic carbon, and organic matter content at all pond hydroperiod classifications and sites. However, the sediment characteristics explaining the most variance differed among sites and hydroperiods and included nitrate concentrations, pH, bulk density, and temperature. We conclude that pond sediments are heterogeneous both within and among ponds in close proximity, and drivers of relatively high CO2 efflux rates differ among pond hydroperiods and elevations. This work emphasizes that local differences can impact predictions of CO2 flux from lentic sediments which are becoming increasingly exposed. [ABSTRACT FROM AUTHOR]

Background: The optimal agent to treat acute agitation in the emergency department (ED) has not been determined. The objective of this study was to compare the effectiveness and safety of intramuscular droperidol, ziprasidone, and lorazepam for acute agitation in the ED. Methods: This was a randomized, double‐blind trial of ED patients with acute agitation requiring parenteral sedation. The study was conducted under exception from informed consent (21 CFR 50.24) from July 2004 to March 2005. Patients were randomized to receive 5 mg of droperidol, 10 mg of ziprasidone, 20 mg of ziprasidone, or 2 mg of lorazepam intramuscularly. We recorded Altered Mental Status Scale (AMSS) scores, nasal end‐tidal carbon dioxide (ETCO2), and pulse oximetry (SpO2) at 0, 15, 30, 45, 60, 90, and 120 minutes as well as QTc durations and dysrhythmias. Respiratory depression was defined as a change in ETCO2 consistent with respiratory depression or SpO2 < 90%. The primary outcome was the proportion of patients adequately sedated (AMSS ≤ 0) at 15 minutes. Results: We enrolled 115 patients. Baseline AMSS scores were similar between groups. For the primary outcome, adequate sedation at 15 minutes, droperidol administration was effective in 16 of 25 (64%) patients, compared to seven of 28 (25%) for 10 mg of ziprasidone, 11 of 31 (35%) for 20 mg of ziprasidone, and nine of 31 (29%) for lorazepam. Pairwise comparisons revealed that droperidol was more effective that the other medications, with 39% (95% confidence interval [CI] = 3% to 54%) more compared to 20 mg of ziprasidone and 33% (95% CI = 8% to 58%) more compared to lorazepam. There was no significant difference between groups in need of additional rescue sedation. Numerically, respiratory depression was lower with droperidol (3/25 [12%]) compared to 10 mg of ziprasidone (10/28 [36%]), 20 mg of ziprasidone (12/31 [39%]), or lorazepam (15/31 [48%]). One patient receiving 20 mg of ziprasidone required intubation to manage an acute subdural hematoma. No patients had ventricular dysrhythmias. QTc durations were similar in all groups. Conclusions: Droperidol was more effective than lorazepam or either dose of ziprasidone for the treatment of acute agitation in the ED and caused fewer episodes of respiratory depression. [ABSTRACT FROM AUTHOR]

A gas blowout during an unauthorized well drilling occurred on June 9, 2020 at the Rome‐Ciampino boundary at the periphery of Colli Albani quiescent volcano. This zone hosts a shallow confined gas‐pressured aquifer, which recently produced further three gas blowouts. Dangerous atmospheric CO2 and H2S concentrations killed some birds, and 12 families were evacuated. The helium isotopic composition indicates that the gas has a magmatic origin. It rises toward the surface along leaky faults, pressurizing the shallow confined aquifer and creating a permanent gas blowout hazard. Colli Albani volcano is characterized by anomalous uplift, release of magmatic gas, and episodic seismic crises. Should a volcanic unrest occur, gas hazard would increase in this densely inhabited zone of Rome city, as the input of magmatic gas into the confined aquifer might create overpressure conditions leading to a harmful phreatic explosion, or increase the emission of hazardous gas through newly created fractures. Plain Language Summary: Rome city is located at the periphery of Colli Albani dormant volcano. Its south‐eastern part hosts a shallow confined gas‐pressurized aquifer, which can produce a gas blowout, that is, a sudden persistent emission of gas and nebulized water, when reached by drillings. Three blowouts were recorded from 2003 to 2016 and a fourth occurred on June 2020. Air concentration of the emitted carbon dioxide and hydrogen sulfide surpassed their Immediately Dangerous to Life and Health limit. Some birds were killed, and 12 families had to be evacuated. The helium isotopic composition confirms that the gas has a deep origin from the Colli Albani magma reservoir. This part of Rome city is permanently exposed to a gas blowout hazard and might be affected either by a phreatic explosion (i.e., without the direct involvement of magma) or by increasing output of hazardous gas through newly created fractures, in case of volcanic unrest at Colli Albani. Key Points: In the SE part of Rome city, a shallow confined gas‐pressurized aquifer produces frequent hazardous gas blowouts from drillingsGas has the highest helium R/Ra of all discharges of the quiescent Colli Albani volcano, indicating a magmatic originIn case of volcanic unrest, a harmful phreatic explosion might occur or the emission of hazardous gas might increase [ABSTRACT FROM AUTHOR]

Summary: Atmospheric carbon dioxide concentration ([CO2]) is increasing, which increases leaf‐scale photosynthesis and intrinsic water‐use efficiency. These direct responses have the potential to increase plant growth, vegetation biomass, and soil organic matter; transferring carbon from the atmosphere into terrestrial ecosystems (a carbon sink). A substantial global terrestrial carbon sink would slow the rate of [CO2] increase and thus climate change. However, ecosystem CO2 responses are complex or confounded by concurrent changes in multiple agents of global change and evidence for a [CO2]‐driven terrestrial carbon sink can appear contradictory. Here we synthesize theory and broad, multidisciplinary evidence for the effects of increasing [CO2] (iCO2) on the global terrestrial carbon sink. Evidence suggests a substantial increase in global photosynthesis since pre‐industrial times. Established theory, supported by experiments, indicates that iCO2 is likely responsible for about half of the increase. Global carbon budgeting, atmospheric data, and forest inventories indicate a historical carbon sink, and these apparent iCO2 responses are high in comparison to experiments and predictions from theory. Plant mortality and soil carbon iCO2 responses are highly uncertain. In conclusion, a range of evidence supports a positive terrestrial carbon sink in response to iCO2, albeit with uncertain magnitude and strong suggestion of a role for additional agents of global change. See also the Commentary on this article by Way et al., 229: 2383–2385. [ABSTRACT FROM AUTHOR]

The high moisture and nutrient contents of spiced beef make it popular with consumers but present challenges for its storage, as spoilage is a common phenomenon. Therefore, for identifying packaging methods to reduce spoilage during storage, this study investigated the effects of 5% O2 (low oxygen), 70% CO2 (high carbon dioxide), and 5% O2/70% CO2/25% N2 (compound group) on lipid oxidation in spiced beef in the test groups and a vacuum‐packed group (control) at storage temperatures of 4, 25, and 60°C. The pH, thiobarbituric acid (TBA), anisidine value (AV), and peroxide value (POV) of the spiced beef were determined. Results indicated that 70% CO2 and storage at 4 and 25°C showed the strongest ability to inhibit the rancidity in spiced beef. The 5% O2 group delayed both initial oxidation and secondary oxidation of lipids. Although the compound group significantly inhibited the rancidity in spiced beef at 60°C, it could not maintain such inhibition for long. Among all the groups, the 70% CO2 group demonstrated maximum inhibition of initial lipid oxidation and suppressed the secondary oxidation of lipids for the longest time. Thus, the modified atmosphere packaging with O2 and CO2 can regulate the fat oxidation in meat products and effectively improve their flavor maintenance. [ABSTRACT FROM AUTHOR]

Infestation with the bird cherry-oat aphid considerably reduced the dry weight yield, the leaf area, the number of tillers and the number of leaves of barley plants. Growth analysis revealed that the major effect of infestation was to reduce unit leaf rate. However, infested plants compensated partially for this by allocating a greater proportion of their dry weight to the production of leaf laminae than did the control plants. Rates of net photosynthesis in individual, attached leaves were measured using the carbon dioxide exchange method; infested and control plants were found to have very similar rates of photosynthesis. Thus the reduction of unit leaf rate did not result from an effect of photosynthesis. It is suggested that the decreased growth of the barley plants is explicable in terms of cumulative assimilate loss due to aphid feeding. [ABSTRACT FROM AUTHOR]

This paper provides an accounting for carbon dioxide emissions arising in Australia by final demand deliveries responsible, using input-output and primary energy input data for 1982-83. Commodities are ranked by emissions per unit and total emissions. It is shown how the methodology employed usefully structures analysis of emissions reductions options, and can compute the system wide implications of specific measures in terms of total emissions. It is established that emissions arising in producing for export are approximately the same as emissions attributable to imports. [ABSTRACT FROM AUTHOR]

A decrease in surface albedo over ice‐covered ocean leads to global warming and Arctic‐amplified warming. Numerical results indicate seasonal variation in Arctic amplification (AA) is a result of local forcing and feedbacks in the Arctic. A decrease in surface albedo leads to a positive feedback, which dominates the local forcing and feedback mechanism. Ocean heat storage in the subsurface acts as a heat forcing to delay the influence of surface albedo feedback. In summer (autumn), heat storage increases (discharges) and contributes to a negative (positive) heat forcing, which decreases (increases) the positive local forcing and feedback and triggers the occurrence of the minimum (maximum) AA. In addition, increased CO2 forcing largely decreases the outgoing longwave radiation at the surface and increases surface temperatures, especially at low latitudes and in the Arctic winters, which decreases the AA magnitude and seasonal variation, although the AA remains nearly the same during winter. Plain Language Summary: The surface albedo over ice‐covered ocean is decreasing, leading to global warming and amplified Arctic warming, which confirms the importance of sea‐ice loss to the Arctic amplification (AA; both formation and seasonal variation). We also study the role of increased CO2 in the seasonal variation in AA by comparing experiments with and without increased CO2, and reveal the direct contribution of CO2 forcing, which is usually neglected.(1)The seasonal variation in Arctic amplification is determined by local forcing and feedback in the Arctic because there is little seasonal variation in the global surface temperature increase and there is nearly no contribution from remote forcing.(2)A positive feedback of surface albedo dominates the radiation flux variation and enhances heat absorption. The Arctic amplification reaches a minimum (maximum) due to the formation (discharge) of heat storage in the subsurface ocean in summer (autumn).(3)Increased CO2 forcing enhances the global surface temperature variation and decreases the Arctic amplification, although it provides a strong positive feedback and nearly keeps Arctic amplification unchanged in winter. Key Points: Contributions from CO2 and surface albedo to Arctic amplification (AA) are discussed individually using numerical experimentsThe seasonal AA variation is controlled by surface albedo feedback and heat storage form/discharge in the subsurface oceanCO2's direct influence weakens AA's magnitude and seasonal variation by inducing stronger warming at low latitudes [ABSTRACT FROM AUTHOR]

Intraspecific variation plays a key role in species' responses to environmental change; however, little is known about the role of changes in environmental quality (the population growth rate an environment supports) on intraspecific trait variation. Here, we hypothesize that intraspecific trait variation will be higher in ameliorated environments than in degraded ones. We first measure the range of multitrait phenotypes over a range of environmental qualities for three strains and two evolutionary histories of Chlamydomonas reinhardtii in laboratory conditions. We then explore how environmental quality and trait variation affect the predictability of lineage frequencies when lineage pairs are grown in indirect co‐culture. Our results show that environmental quality has the potential to affect intraspecific variability both in terms of the variation in expressed trait values, and in terms of the genotype composition of rapidly growing populations. We found low phenotypic variability in degraded or same‐quality environments and high phenotypic variability in ameliorated conditions. This variation can affect population composition, as monoculture growth rate is a less reliable predictor of lineage frequencies in ameliorated environments. Our study highlights that understanding whether populations experience environmental change as an increase or a decrease in quality relative to their recent history affects the changes in trait variation during plastic responses, including growth responses to the presence of conspecifics. This points toward a fundamental role for changes in overall environmental quality in driving phenotypic variation within closely related populations, with implications for microevolution. [ABSTRACT FROM AUTHOR]

Climate change will affect both the mean state and seasonality of marine physical and biogeochemical properties, with important implications for the oceanic sink of atmospheric CO2. Here, we investigate the seasonal cycle of the air‐sea exchange of CO2 and pCO2,sw (surface seawater pCO2) and their long term changes using the CMIP6 submission of the NASA‐GISS modelE (GISS‐E2.1‐G). In comparison to the CMIP5 submission (GISS‐E2‐R), we find that on the global scale, the seasonal cycles of the CO2 flux and NPP have improved, while the seasonal cycles of dissolved inorganic carbon (DIC), alkalinity, and macronutrients have deteriorated. Moreover, for all ocean biogeochemistry fields, changes in skill between E2.1‐G and E2‐R display large regional variability. For E2.1‐G, we find similar modeled and observed CO2 flux seasonal cycles in the subtropical gyres, where seasonal anomalies of pCO2,sw and the flux are temperature‐driven, and the Southern Ocean, where anomalies are DIC‐driven. Biases in these seasonal cycles are largest in the subpolar and equatorial regions, driven by a combination of biases in temperature, DIC, alkalinity, and wind speed. When comparing the historical simulation to a simulation with an idealized increase in atmospheric pCO2, we find that the seasonal amplitudes of the CO2 flux and pCO2,sw generally increase. These changes are produced by increases in the sensitivity of pCO2,sw to its respective drivers. These findings are consistent with the notion that the seasonality of pCO2,sw is expected to increase due to the increase of atmospheric pCO2, with changes in the seasonality of temperature, DIC, and alkalinity having secondary influences. Plain Language Summary: The ocean plays an important role in removing human CO2 emissions from the atmosphere. The removal varies seasonally, and this variability is expected to change as the ocean's carbon content increases. To predict these changes, models need to accurately simulate seasonal changes of the air‐sea exchange of CO2. In this study, we examine the seasonal cycle of the air‐sea exchange of CO2 in the CMIP6 version of the NASA‐GISS modelE (GISS‐E2.1‐G). We find good agreement between the seasonal cycles in the model and observations in the subtropical latitudes, where seasonal changes are mainly caused by temperature changes, and in the Southern Ocean, where seasonal changes are mainly caused by changes in dissolved inorganic carbon (DIC). Agreement is much poorer in high latitudes and tropical waters, where discrepancies in model wind speed, temperature, DIC, and alkalinity all contribute to differences between the modeled and observed seasonal cycle of air‐sea CO2 exchange. We further find, under future atmospheric CO2 increase, that seasonal extremes in the air‐sea exchange of CO2 increase in most of the ocean. Our findings support the idea that, under increased CO2 levels, the change in the ocean's ability to take CO2 from the atmosphere will be seasonally dependent. Key Points: The seasonality of the CO2 flux, pCO2, and their drivers in the NASA‐GISS model are evaluated using a suite of monthly climatologiesThe seasonal cycles of the CO2 flux and pCO2, sw are temperature‐driven in the subtropics and DIC‐driven in the Southern OceanIn an idealized future forcing scenario, changes in the flux are largely driven by changes in the sensitivity of pCO2 to its drivers [ABSTRACT FROM AUTHOR]

The chemical equilibrium analysis of various possible reactions involved in the five CO2‐based routes for the synthesis of dimethyl carbonate (DMC), a green chemical reagent, was performed in the present study. The variation of the molar Gibbs free energy change with temperature for the major reactions of DMC synthesis in all five routes was studied in the specified temperature range of 298.15 K‐453.15 K and at both 1 bar and 28 bar pressures (1 bar = 105 Pa) to observe the thermodynamic favourability of all routes. To observe the temperature effect, the molar heat capacities for various compounds were estimated in terms of temperature. A second‐order group additivity method called the Ruzicka‐Domalski method was used to estimate these heat capacity values. The major reactions of DMC synthesis in urea methanolysis, EC transesterification, PC transesterification, and direct CO2 synthesis routes were compared by investigating the effect of temperature (in the range of 298.15 K‐453.15 K) on the chemical equilibrium constants and the equilibrium conversions of methanol at a constant pressure of 28 bar. The one‐pot propylene oxide (PO) synthesis route was observed to be better among all the five CO2 based routes when it was compared with respect to values of the chemical equilibrium constant and equilibrium conversion of methanol at standard conditions. The reliability of the EC transesterification route was found better among all the routes at initial conditions (T = 298.15 K; P = 28 bar). While the urea methanolysis route was found as least favourable at initial conditions. [ABSTRACT FROM AUTHOR]

Objective: Insufflation of the amniotic cavity with carbon dioxide (CO2) is used clinically to improve visibility during complex fetoscopic surgery. Insufflation with heated, humidified CO2 has recently been shown to reduce fetal hypercapnia and acidosis in sheep, compared with use of cold and dry CO2, but the underlying mechanisms are unclear. The aim of this study was to investigate whether differences in placental CO2 and oxygen (O2) exchange during insufflation with heated and humidified vs cold and dry CO2 could explain these findings. Methods: Thirteen fetal lambs at 105 days of gestation (term, 146 days) were exteriorized partially, via a midline laparotomy and hysterotomy, and instrumented with an umbilical artery catheter, an umbilical vein catheter and a common umbilical vein flow probe. Arterial and venous catheters and flow probes were also inserted into the maternal uterine circulation. Six ewes were insufflated with cold, dry CO2 (22°C; 0–5% humidity) and seven with heated, humidified CO2 (40°C; 95–100% humidity) at 15 mmHg for 180 min. Blood‐flow recordings and paired arterial and venous blood gases were sampled from uterine and umbilical vessels. Rates of placental CO2 and O2 exchange were calculated. Results: After 180 min of insufflation, fetal survival was 33% (2/6) using cold, dry CO2 and 71% (5/7) using heated, humidified CO2. By 120 min, fetuses insufflated with heated, humidified CO2 had lower arterial CO2 levels and higher arterial pH compared to those insufflated with cold, dry gas. Insufflation decreased significantly placental gas exchange in both groups, as measured by rates of both (i) fetal CO2 clearance and O2 uptake and (ii) maternal O2 delivery and CO2 uptake from the fetal compartment. Conclusions: Lower arterial CO2 and higher pH levels in fetuses insufflated with heated and humidified, compared to cold and dry, CO2 could not be explained by differences in placental gas exchange. Instead, heated and humidified insufflation appeared to reduce fetal CO2 absorption from the uterus, supporting its use in preference to cold, dry CO2. © 2019 International Society of Ultrasound in Obstetrics and Gynecology [ABSTRACT FROM AUTHOR]

Key points: A moderate increase in PCO2 (55 mmHg) closes Cx26 gap junctions.This effect of CO2 is independent of changes in intra‐ or extracellular pH.The CO2‐dependent closing effect depends on the same residues (K125 and R104) that are required for the CO2‐dependent opening of Cx26 hemichannels.Pathological mutations of Cx26 abolish the CO2‐dependent closing of the gap junction.Elastic network modelling suggests that the effect of CO2 on Cx26 hemichannels and gap junctions is mediated through changes in the lowest entropy state of the protein. Cx26 hemichannels open in response to moderate elevations of CO2 (PCO2 55 mmHg) via a carbamylation reaction that depends on residues K125 and R104. Here we investigate the action of CO2 on Cx26 gap junctions. Using a dye transfer assay, we found that an elevated PCO2 of 55 mmHg greatly delayed the permeation of a fluorescent glucose analogue (NBDG) between HeLa cells coupled by Cx26 gap junctions. However, the mutations K125R or R104A abolished this effect of CO2. Whole cell recordings demonstrated that elevated CO2 reduced the Cx26 gap junction conductance (median reduction 66.7%, 95% CI, 50.5–100.0%) but had no effect on Cx26K125R or Cx31 gap junctions. CO2 can cause intracellular acidification. Using 30 mm propionate, we found that acidification in the absence of a change in PCO2 caused a median reduction in the gap junction conductance of 41.7% (95% CI, 26.6–53.7%). This effect of propionate was unaffected by the K125R mutation (median reduction 48.1%, 95% CI, 28.0–86.3%). pH‐dependent and CO2‐dependent closure of the gap junction are thus mechanistically independent. Mutations of Cx26 associated with the keratitis ichthyosis deafness syndrome (N14K, A40V and A88V), in combination with the mutation M151L, also abolished the CO2‐dependent gap junction closure. Elastic network modelling suggests that the lowest entropy state when CO2 is bound is the closed configuration for the gap junction but the open state for the hemichannel. The opposing actions of CO2 on Cx26 gap junctions and hemichannels thus depend on the same residues and presumed carbamylation reaction. Key points: A moderate increase in PCO2 (55 mmHg) closes Cx26 gap junctions.This effect of CO2 is independent of changes in intra‐ or extracellular pH.The CO2‐dependent closing effect depends on the same residues (K125 and R104) that are required for the CO2‐dependent opening of Cx26 hemichannels.Pathological mutations of Cx26 abolish the CO2‐dependent closing of the gap junction.Elastic network modelling suggests that the effect of CO2 on Cx26 hemichannels and gap junctions is mediated through changes in the lowest entropy state of the protein. [ABSTRACT FROM AUTHOR]

Cementitious ceramics, produced from the hydration of cement and hydrated lime, are responsible for a great deal of damage to the environment due to the high emission of CO2 that occurs in the production of cement and lime. Therefore, the objective of this work was to substitute the hydrated lime with a combination of clay residue and marble waste extracted from ceramic and ornamental rock producing industries, respectively, which constitutes a circular economy for the ceramic industry related to masonry applications. Ceramics were produced in the proportion 1:1:6:1.5 (cement:lime:sand:water), through the molding procedure, and were studied by replacing hydrated lime with 100% clay residue and 100% marble residue, in addition to stoichiometric calculated parts of marble to clay. The molar ratios used were 1:1, 1:2, and 2:1 (marble:clay). Tests of consistency, incorporated air content, water retention, compression strength, density, water absorption by capillarity, adhesion, and electrical resistivity were performed. The results obtained demonstrate that the use of residue of marble and clay together, as long as they are correctly balanced, provides a high gain in technological properties, enabling the circular economy of cementitious ceramics, mainly for the composition 1 marble:1clay, which presented the best properties, both in the fresh and hardened state. The economic analysis carried out proved the financial gains for the industrial sectors involved (civil construction, ornamental rock, and ceramic). [ABSTRACT FROM AUTHOR]

We report here an increase in the amount of carbon dioxide in Taal lake during the year preceding the January 2020 eruption. Starting in February 2019, the CO2 emissions from the lake increased from background value (700 t day−1) to a flux close to 2,400 t day−1 at the time of the eruption. We show that the lake acts as a highly sensitive gasometer where CO2 (aq) reflects the balance between CO2 supplied to the lake (by hot springs) and CO2 lost by diffusion at air‐water interface. The lake waters are extremely enriched in dissolved carbon dioxide with pCO2 values as high as 0.35 atm (350,000 ppmV) equivalent to a CO2(aq) of 9.32 mmol l−1. The residence time of CO2 in the lake is around 1 week which allows for fast detection of change in magma degassing and makes carbon dioxide a very promising tool for volcano monitoring. Plain Language Summary: Volcanic gas fuels volcanic eruptions. Among the dominant species, sulfur dioxide is easily monitored using remote sensing and ground‐based instruments. Carbon dioxide remains however challenging to detect and quantify due to its high background in the atmosphere. We have developed a new methodology for monitoring CO2 by using a volcanic lake in an innovative way. It allows to quantify CO2 emissions by the lake, thereby providing critical insights into the change in degassing magma at depth. Using this new methodology, we were able to detect the earlier precursory signs of the January 2020 eruption of Taal volcano in the Philippines which affected over 380,000 people from local communities. The Taal volcanic lake is a unique location to study CO2 emission with spectacular degassing from more than 500 subaqueous vents that were active for many years. The lake waters are extremely enriched in carbon dioxide, to our knowledge, the highest value ever recorded in a lake. Our method also provides the longest time series to date of continuous CO2 emission from a volcano. Key Points: pCO2 in a volcanic lake reflects the balance between magmatic CO2 supplied by hot springs and CO2 lost by diffusion to the atmosphereThe continuous monitoring of CO2 flux by the volcanic lake is achieved using in situ measurement of lake pCO2 with a unique sensorThe increase in pCO2 in Taal volcanic lake is a precursory sign of the January 2020 eruption [ABSTRACT FROM AUTHOR]

This study applies Orbiting Carbon Observatory‐2 (OCO‐2) column‐averaged dry‐air mole fractions of CO2 (XCO2) to constrain CO2 fluxes during the 2018 Kilauea volcano eruption. CO2 enhancements (ΔXCO2) of 1–2 parts per million were observed far downwind of the eruption coincident with elevated sulfur dioxide (SO2) concentrations. The estimated CO2 emission rate was 77.1 ± 49.6 kilotons per day (kt day−1) on 11 July 2018 with most of the uncertainty from modeled winds and XCO2 retrievals. This emission rate is higher compared to flux estimates made with ground‐based measurements (30–40 kt day−1). However, cross‐sectional flux estimates made using OCO‐2 XCO2 observations will inherently be larger than ground‐based measurements near the source as these estimates comprise all sources of CO2 in the vicinity of the eruption (e.g., vegetation and soil burning). This study for the first time uses satellite XCO2 data ~200 km downwind to estimate CO2 emissions from a major volcanic eruption. Plain Language Summary: Carbon dioxide (CO2) is a greenhouse gas that plays a predominant role in climate change. Volcanoes emit CO2 and play a role in the global carbon cycle; however, the amount of CO2 they emit is highly uncertain. One of the main reasons for this uncertainty is the limited amount of volcanic emission measurements available to estimate these CO2 emissions. Satellites retrieving CO2 have an advantage over ground‐based measurements as they have the potential to obtain data over the entire globe. After the launch of National Aeronautics and Space Administration (NASA)'s Orbiting Carbon Observatory‐2 (OCO‐2) satellite in 2014, spaceborne observations of volcanic CO2 were possible. This study uses OCO‐2 measurements of CO2 to estimate emissions during the 2018 Kilauea volcano eruption and is the first to trace satellite CO2 data downwind from the source of a major volcanic eruption. Here we show that the Kilauea volcano eruption emitted large amounts of CO2 and OCO‐2 proved capable to observe the large atmospheric concentrations associated with these emissions. Key Points: Orbiting Carbon Observatory‐2 retrievals were applied to estimate CO2 emissions during the 2018 Kilauea volcano eruptionA CO2 emission rate of 77.1 ± 49.6 kt day−1 was estimated from volcanic and other emission sources on 11 July 2018This study is the first attempt to use satellite retrieved CO2 data far downwind of a major volcanic eruption to estimate emissions [ABSTRACT FROM AUTHOR]

Summary: Rising atmospheric CO2 (ca) is expected to promote tree growth and lower water loss via changes in leaf gas exchange. However, uncertainties remain if gas‐exchange regulation strategies are homeostatic or dynamical in response to increasing ca, as well as evolving climate and pollution inputs.Using a suite of tree ring‐based δ13C‐derived physiological parameters (Δ13C, ci, iWUE) and tree growth from a mesic, low elevation stand of canopy‐dominant Tsuga canadensis in north‐eastern USA, we investigated the influence of rising ca, climate and pollution on, and characterised the dynamical regulation strategy of, leaf gas exchange at multidecadal scales.Isotopic and growth time series revealed an evolving physiological response in which the species shifted its leaf gas‐exchange strategy dynamically (constant ci; constant ci/ca; constant ca − ci) in response to rising ca, moisture availability and site conditions over 111 yr. Tree iWUE plateaued after 1975, driven by greater moisture availability and a changing soil biogeochemistry that may have impaired a stomatal response.Results suggested that trees may exhibit more complex physiological responses to the changing environmental conditions over multidecadal periods, and complicating the parameterisation of Earth system models and the estimation of future carbon sink capacity and water balance in midlatitude forests and elsewhere. [ABSTRACT FROM AUTHOR]

Summary: C2 photosynthesis is a carbon concentrating mechanism that can increase net CO2 assimilation by capturing, concentrating and re‐assimilating CO2 released by photorespiration. Empirical and modelling studies indicate that C2 plants assimilate more carbon than C3 plants under high temperature, bright light, and low CO2 conditions. I argue that engineering C2 photosynthesis into C3 crops is a promising approach to improve photosynthetic performance under these – and temporally heterogeneous – environments, and review the modifications that may re‐create a C2 phenotype in C3 plants. Although a C2 engineering program would encounter many of the same challenges faced by C4 engineering programmes, the simpler leaf anatomical requirements make C2 engineering a feasible approach to improve crops in the medium term. [ABSTRACT FROM AUTHOR]

Tracers are used to tag the injected carbon dioxide (CO2) for verification of the storage performance and containment in geosequestration. Yet the characterization of the transport behavior of a chemical tracer in two‐phase flow system has not been fully investigated. We present experimental observations together with numerical results for both homogeneous and heterogeneous media from core scale to field scale. The key features of the breakthrough curves (BTCs) that include the tracer arrival time, peak concentration, and tailing pattern were examined. We identify distinct differences in BTCs depending on whether the formation was previously swept by CO2. When the tracer is released before CO2 sweeps the formation, the tracer transports at the front of gas‐liquid interfaces with a narrow tracer plume distribution and the BTCs reflect the effect of local heterogeneity. Furthermore, a series of tracer pulse can be used to identify whether new pathways have been developed during CO2 injection. Plain Language Summary: Geologic storage of carbon dioxide (CO2) has become an attractive climate change mitigation option, and ensuring the containment of injected CO2 is of prime importance for successful geological storage. Tracers are an effective means of tracking injected CO2 and verifying containment within the storage formation. Here we show that distinctive features in observed tracer data are highly related to whether or not the storage formation was previously swept by CO2. When the tracer is released at the beginning of CO2 injection, the tracer moves with narrow distribution and is advantageous for the tracer data to reflect multiple pathways. By contrast, once the CO2 sweeps the formation, the tracer moves much faster with a wider dispersion pattern. Key Points: We present experimental observations with numerical results for characterizing the tracer transport behavior in two‐phase flow systemThe key features of breakthrough curves and tracer velocity highly depend on whether the formation was previously swept by CO2A series of tracer pulse can be used to identify whether new pathways have been developed during CO2 injection [ABSTRACT FROM AUTHOR]

Interactions between riverine inputs, internal cycling, and oceanic exchange result in dynamic variations in the partial pressure of carbon dioxide (pCO2) in large estuaries. Here, we report the first bay‐wide, annual‐scale observations of surface pCO2 and air–water CO2 flux along the main stem of the Chesapeake Bay, revealing large annual variations in pCO2 (43–3408 μatm) and a spatial‐dependence of pCO2 on internal and external drivers. The low salinity upper bay was a net source of CO2 to the atmosphere (31.2 mmol m−2 d−1) supported by inputs of CO2‐rich Susquehanna River water and the respiration of allochthonous organic matter, but part of this region was also characterized by low pCO2 during spring and fall phytoplankton blooms. pCO2 decreased downstream due to CO2 ventilation supported by long water residence times, stratification, mixing with low pCO2 water masses, and carbon removal by biological uptake. The mesohaline middle bay was a net CO2 sink (−5.8 mmol m−2 d−1) and the polyhaline lower bay was nearly in equilibrium with the atmosphere (1.0 mmol m−2 d−1). Although the main stem of the bay was a weak CO2 source (3.7 ± 3.3 × 109 mol C) during the dry hydrologic (calendar) year 2016, our observations showed higher river discharge could decrease CO2 efflux. In contrast to many other estuaries worldwide that are strong sources of CO2 to the atmosphere, the Chesapeake Bay and potentially other large estuaries are very weak CO2 sources in dry years, and could even turn into a CO2 sink in wet years. [ABSTRACT FROM AUTHOR]

Long‐term multigenerational experimental simulations of climate change on insect pests of economically and socially important crops are crucial to anticipate challenges for feeding humanity in the not‐so‐far future. Mexican bean weevil Zabrotes subfasciatus, is a worldwide pest that attacks the common bean Phaseolus vulgaris seeds, in crops and storage. We designed a long term (i.e., over 10 generations), experimental simulation of climate change by increasing temperature and CO2 air concentration in controlled conditions according to model predictions for 2100. Higher temperature and CO2 concentrations favored pest's egg‐to‐adult development survival, even at high female fecundity. It also induced a reduction of fat storage and increase of protein content but did not alter body size. After 10 generations of simulation, genetic adaptation was detected for total lipid content only, however, other traits showed signs of such process. Future experimental designs and methods similar to ours, are key for studying long‐term effects of climate change through multigenerational experimental designs. [ABSTRACT FROM AUTHOR]

Institutions in a country ensure sustainability and play a significant role in economic development by encouraging best practices in governmental interventions. A strong and transparent institutional framework opposes corruption and improves the management of public finances, which may also yield desired outcomes for the environment and society. However, the role of institutions in environmental issues is still under‐investigated in the literature. This study aims to investigate the relationship between renewable energy consumption, institutional quality, economic performance, and carbon dioxide (CO2) emissions in 18 Asia‐Pacific Economic Cooperation (APEC) countries for the period 1992–2015. To this end, robust panel data estimation techniques are employed. The study confirms that a cointegration relationship exists among study variables. Evidence from the empirical results reveals that institutions have beneficial environmental effects. Likewise, renewable energy reduces carbon emissions to mitigate climate change, but nonrenewable energy harms the environment. Institutional quality helps to form the environmental Kuznets curve hypothesis in APEC countries. Finally, causality analysis refers to the unidirectional causality running from institutional quality to CO2 emissions. Results reveal that stronger institutional arrangements in APEC countries could be the solution for implementations of effective environmental regulation to combat rising environmental challenges without sacrificing higher economic growth. [ABSTRACT FROM AUTHOR]

As a profitable product from CO2 electroreduction, HCOOH holds economic viability only when the selectivity is higher than 90% with current density (j) over −200.0 mA cm−2. Herein, Bi@Sn core–shell nanoparticles (Bi core and Sn shell, denoted as Bi@Sn NPs) are developed to boost the activity and selectivity of CO2 electroreduction into HCOOH. In an H‐cell system with 0.5 m KHCO3 as electrolyte, Bi@Sn NPs exhibit a Faradaic efficiency for HCOOH (FEHCOOH) of 91% with partial j for HCOOH (jHCOOH) of −31.0 mA cm−2 at −1.1 V versus reversible hydrogen electrode. The potential application of Bi@Sn NPs is testified via chronopotentiometric measurements in the flow‐cell system with 2.0 m KHCO3 electrolyte. Under this circumstance, Bi@Sn NPs achieve an FEHCOOH of 92% with an energy efficiency of 56% at steady‐state j of −250.0 mA cm−2. Theoretical studies indicate that the energy barrier of the potential‐limiting step for the formation of HCOOH is decreased owing to the compressive strain in the Sn shell, resulting in the enhanced catalytic performance. [ABSTRACT FROM AUTHOR]

Optimizing crops to improve light absorption and CO2 assimilation throughout the canopy is a proposed strategy to increase yield and meet the needs of a growing population by 2050. Globally, the greatest population increase is expected to occur in Sub‐Saharan Africa where large yield gaps currently persist; therefore, it is crucial to develop high‐yielding crops adapted to this region. In this study, we screened 50 cowpea (Vigna unguiculata (L.) Walp) genotypes from the multi‐parent advanced generation inter‐cross (MAGIC) population for canopy architectural traits, canopy photosynthesis, and water‐use efficiency using a canopy gas exchange chamber in order to improve our understanding of the relationships among those traits. Canopy architecture contributed to 38.6% of the variance observed in canopy photosynthesis. The results suggest that the light environment within the canopy was a limiting factor for canopy CO2 assimilation. Traits favoring greater exposure of leaf area to light such as the width of the canopy relative to the total leaf area were associated with greater canopy photosynthesis, especially in canopies with high biomass. Canopy water‐use efficiency was highly determined by canopy photosynthetic activity and therefore canopy architecture, which indicates that optimizing the canopy will also contribute to improving canopy water‐use efficiency. We discuss different breeding strategies for future programs aimed at the improvement of cowpea yield for the Sub‐Saharan African region. We show that breeding for high biomass will not optimize canopy CO2 assimilation and suggest that selection should include multiple canopy traits to improve light penetration. [ABSTRACT FROM AUTHOR]

Global mangrove loss is occurring from deforestation and extreme climatic events, but changes to the coastal carbon cycle following mangrove mortality and/or loss are not well understood. In 2015/2016, a massive climate‐driven mangrove dieback event occurred over ~ 1000 km of Australian coastline. To assess carbon loss following mortality, carbon fluxes in adjacent living and dead forest areas were compared 8 and 20 months postforest dieback. Dead areas experienced an increase in soil CO2 efflux by ~ 189%, and a decrease in oceanic dissolved inorganic carbon (DIC) outwelling of ~ 50% relative to living areas. DIC outwelling (predominantly carbonate alkalinity) and soil CO2 efflux accounted for 81% and 16% of losses from the living forest, in comparison to 51% and 47%, respectively, from the dead forest. The dieback drove a shift from a dominance of oceanic carbon outwelling to increased atmospheric CO2 emissions and decreased alkalinity exports. This shift was likely driven by increased oxygen sediment permeation and the loss of mangrove net primary productivity. Combining our new observations with literature data, we found a logarithmic relationship between soil carbon loss and time since mangrove loss. Using this relationship, we estimate ongoing global carbon losses from historical mangrove deforestation and dieback could be 13.7 ± 9.4 Tg C yr−1, which is eightfold higher than previous estimates and offsets global mangrove carbon burial by ~ 60%. Even if no future deforestation occurred, we estimate ongoing carbon losses to the atmosphere and ocean from current global mangrove losses of 27 Tg C over the next 30 yr. [ABSTRACT FROM AUTHOR]

We examine the response of the Community Earth System Model Versions 1 and 2 (CESM1 and CESM2) to abrupt quadrupling of atmospheric CO2 concentrations (4xCO2) and to 1% annually increasing CO2 concentrations (1%CO2). Different estimates of equilibrium climate sensitivity (ECS) for CESM1 and CESM2 are presented. All estimates show that the sensitivity of CESM2 has increased by 1.5 K or more over that of CESM1. At the same time the transient climate response (TCR) of CESM1 and CESM2 derived from 1%CO2 experiments has not changed significantly—2.1 K in CESM1 and 2.0 K in CESM2. Increased initial forcing as well as stronger shortwave radiation feedbacks are responsible for the increase in ECS seen in CESM2. A decomposition of regional radiation feedbacks and their contribution to global feedbacks shows that the Southern Ocean plays a key role in the overall behavior of 4xCO2 experiments, accounting for about 50% of the total shortwave feedback in both CESM1 and CESM2. The Southern Ocean is also responsible for around half of the increase in shortwave feedback between CESM1 and CESM2, with a comparable contribution arising over tropical ocean. Experiments using a thermodynamic slab‐ocean model (SOM) yield estimates of ECS that are in remarkable agreement with those from fully coupled Earth system model (ESM) experiments for the same level of CO2 increase. Finally, we show that the similarity of TCR in CESM1 and CESM2 masks significant regional differences in warming that occur in the 1%CO2 experiments for each model. Plain Language Summary: Computer models of the Earth's climate system are complex. Our best guess scenarios for how the climate system will change due to human activity over the next century are also complex. They include estimates of changing greenhouse gas (e.g., CO2) levels in the atmosphere, aerosol (e.g., smog and haze) emissions, and land use changes (e.g., deforestation and urbanization). To help understand this complex system, the climate modeling community has designed two simplified experiments: abrupt CO2 quadrupling (4xCO2) and 1% annual CO2 increase (1%CO2). In these experiments all human‐induced factors in the climate system are held constant (at preindustrial levels) except for CO2 in the atmosphere. Results of these experiments from different climate models can be compared to gain insight into the climate system. We look at two versions of the Community Earth System Model (CESM1 and CESM2). The warming simulated in the 4xCO2 experiment (climate sensitivity) has increased substantially in CESM2. This is related to changes in clouds over the Southern Ocean and tropics. At the same time warming in in the 1%CO2 experiment has not increased. This is related to differences in how CESM1 and CESM2 simulate northern oceans (Arctic, North Atlantic, and North Pacific). Key Points: Climate sensitivity has increased from 4 K to over 5 K in CESM2 compared to CESM1Shortwave radiation feedbacks over the Southern Ocean play a key role in determining the response of CESM to increasing CO2Various measures of climate response, including equilibrium climate sensitivity (ECS) and transient climate response (TCR), are not simply related in CESM [ABSTRACT FROM AUTHOR]

Storing CO2 in geological formations can reduce the amount of greenhouse gases in the atmosphere. In order to explore the fracture behavior of caprock during CO2 geological storage, three caprock adsorption experiments for supercritical, liquid, and gaseous CO2 were designed. The fracture toughness of mode I, mode II, and mixed‐mode I/II of sandstone before and after the experiment was tested, and X‐ray diffraction (XRD), X‐ray fluorescence (XRF), and scanning electron microscopy (SEM) were used to examine the fracture mechanical characteristics of sandstone. Results showed that the pure mode I fracture toughness of sandstone immersed in supercritical CO2 (ScCO2), liquid CO2, and gaseous CO2 for 30 days decreased by 27.89%, 11.01%, and 17.43%, respectively, compared to nonimmersed sandstone. Pure mode I fracture toughness was more sensitive than mixed‐mode I/II and pure mode II fracture toughness to the various CO2 phase states. Furthermore, the ability of sandstone to resist fracture and failure was significantly reduced by the adsorption of CO2 in different phases. The effects of the different phases were in the following order: ScCO2 > gaseous CO2 > liquid CO2. The decreased ability of sandstone to resist fracture was primarily due to the geophysical and chemical reactions between CO2 and minerals, the alteration of minerals, or the formation of new substances. SEM observations showed that liquid CO2 adsorption caused the sandstone to undergo intergranular fracture, and the adsorption of gaseous CO2 promoted the occurrence of transgranular fractures. In particular, due to the ScCO2 adsorption, various fracture forms such as intergranular fractures, transgranular fractures, and mutual coupling fractures existed simultaneously. Sandstone exhibited numerous fractures and pores, and fracture resistance was weakened. Results of this study have important significance for evaluating the stability and safety of CO2 geological storage. [ABSTRACT FROM AUTHOR]

Absorption and capture of CO2 directly from sources represents one of the major tools to reduce its emission in the troposphere. One of the possibilities is to incorporate CO2 inside a liquid exploiting its propensity to react with amino groups to yield carbamic acid or carbamates. A particular class of ionic liquids, based on amino acids, appear to represent a possible efficient medium for CO2 capture because, at difference with current industrial setups, they have the appeal of a biocompatible and environmentally benign solution. We have investigated, by means of highly accurate computations, the feasibility of the reaction that incorporates CO2 in an amino acid anion with a protic side chain and ultimately transforms it into a carbamate derivative. Through an extensive exploration of the possible reaction mechanisms, we have found that different prototypes of amino acid anions present barrierless reaction mechanisms toward CO2 absorption. [ABSTRACT FROM AUTHOR]

The refrigerant trans‐1,3,3,3‐tetrafluoropropene (HFO‐1234ze) is used as a replacement for former cooling agents that have been phased‐out due to their global warming potential or ozone depleting potential. Although it is used on a large scale, only a few vibrational data and no structural data of HFO‐1234ze are known. We report structure determinations based on low‐temperature single‐crystal X‐ray diffraction data as well as gas‐phase diffraction data of HFO‐1234ze and HFO‐1234yf (2,3,3,3‐tetrafluoropropene). Furthermore, vibrational spectra of HFO‐1234ze in all phases are described. The results are discussed together with quantum‐chemical calculations on the PBE0/cc‐pVTZ level of theory. Combustion experiments of HFO‐1234ze show carbonyl difluoride, carbon dioxide and hydrogen fluoride to be the main combustion products. [ABSTRACT FROM AUTHOR]

The author discusses the role of coccolithophore Emiliania huxleyi (E. huxleyi) in ocean acidification. He says that E. huxleyi accounts on global ocean calcium carbonate production. Also investigated is the study conducted by L. T. Bach and colleagues which shows that E. huxleyi provides evidence on carbon concentrating mechanism (CCM) that is not driven by calcification and suggests that E. huxleyi growth in marine system is not stimulated by carbon dioxide as the climate change progresses.

The article comments on a study of lateral diffusion of carbon dioxide conducted by R. Pieruschka et al and published in a 2006 issue of "New Phytologist." It outlines the major arguments of the study and presents a discussion on leaf anatomy and patchy stomata behavior of leaves. It considers the importance of lateral carbon dioxide diffusion.

We use several global coupled atmosphere‐ocean‐biogeochemistry models from the Coupled Model Intercomparison Project (CMIP5) to show that the global interannual variability of the sea surface pCO2 (calculated as 1σ) will increase by ∼64 ± 20% by 2040–2090 relative to the beginning of the industrial revolution under the RCP8.5 scenario. All models agree that the increase in variability is a consequence of a larger background pCO2 and a lower buffering capacity that enhance the response of pCO2 to the fluctuations of surface temperature (T) and dissolved inorganic carbon (DIC). The most skillful group of models under present‐day conditions shows a future global decrease in DIC fluctuations that will weaken the pCO2 interannual variability (IAV). The remaining uncertainties in the projected evolution of pCO2 variability regionally highlight the need for continuous carbon monitoring programs which will contribute to a better understanding of the oceanic carbon sink's response to increased green house emissions. Plain Language Summary: We used a series of coupled climate/carbon cycle models to show that the year‐to‐year variations in the oceanic surface partial pressure of carbon dioxide will intensify by the end of the 21st century. The future interannual fluctuations in carbonate chemistry will have a stronger impact on surface ocean pCO2, because anthropogenic carbon emissions make the ocean less able to buffer these natural changes. Earth system models also document and overall weakening of the underlying biophysical interannual changes, which can partly compensate for the enhancement of pCO2 in some areas, such as the eastern equatorial Pacific. Projected changes in the ocean's carbon dioxide levels will also impact the flux of carbon between the atmosphere and the ocean and therefore play an important role in the uptake of anthropogenic carbon and the level of future greenhouse warming. Key Points: The interannual oceanic pCO2 variability is amplified by 2040–2090 in most of the world's oceans, except in the equatorial PacificThe amplification in pCO2 variability is due to an increased oceanic sensitivity to dissolved inorganic carbon and temperature variationsA decrease of the dissolved inorganic carbon fluctuations counteracts the amplification, but models differ in this projection [ABSTRACT FROM AUTHOR]

For three decades, advocates for climate change policy have simultaneously emphasized the urgency of taking ambitious actions to mitigate greenhouse gas (GHG) emissions and provided false reassurances of the feasibility of doing so. The policy prescription has relied almost exclusively on a single approach: reduce emissions of carbon dioxide (CO2) and other GHGs. Since 1990, global CO2 emissions have increased 60%, atmospheric CO2 concentrations have raced past 400 ppm, and temperatures increased at an accelerating rate. The one‐prong strategy has not worked. After reviewing emission mitigation's poor performance and low‐probability of delivering on long‐term climate goals, we advance a three‐pronged strategy for mitigating climate change risks: adding adaptation and amelioration—through solar radiation management (SRM)—to the emission mitigation approach. We highlight SRM's potential, at dramatically lower cost than emission mitigation, to play a key role in offsetting warming. We address the moral hazard reservation held by environmental advocates—that SRM would diminish emission mitigation incentives—and posit that SRM deployment might even serve as an "awful action alert" that galvanizes more ambitious emission mitigation. We conclude by emphasizing the value of an iterative act‐learn‐act policy framework that engages all three prongs for limiting climate change damages. [ABSTRACT FROM AUTHOR]

Most global climate models project a considerable stratospheric moistening during global warming. It is important to quantify how significantly the increase of stratospheric humidity affects the radiation budget and contributes to the surface warming. Here, we conduct a mechanism denial experiment to investigate the warming effect of the stratospheric water vapor (SWV) using a global climate model. By locking the SWV in a quadrupling CO2 experiment, we find that the surface warming effect of SWV is not as significant as previously thought, increasing the global mean surface warming by about 2%. This is due to compensating changes in other feedback, especially those of tropospheric temperature and cloud, affected by SWV. Plain Language Summary: How significantly does the increase of stratospheric humidity as projected by many global climate models contribute to the surface warming? Here, we conduct a mechanism denial experiment to address this question. By locking the SWV in a quadrupling CO2 experiment, we find that the warming effect of SWV is not as significant as previously thought, due to compensating changes in other feedback. Key Points: Locking experiment suggests a weaker stratospheric water vapor feedback than previously thoughtTropospheric feedback are coupled with the stratospheric water vapor feedbackThe coupling limits the surface warming effect of stratospheric water vapor [ABSTRACT FROM AUTHOR]

The application of organic materials to soil can recycle nutrients and increase organic matter in agricultural lands. Digestate can be used as a nutrient source for crop production but it has also been shown to stimulate greenhouse gas (GHG) emissions from amended soils. While edaphic factors, such as soil texture and pH, have been shown to be strong determinants of soil GHG fluxes, the impact of the legacy of previous management practices is less well understood. Here we aim to investigate the impact of such legacy effects and to contrast them against soil properties to identify the key determinants of soil GHG fluxes following digestate application. Soil from an already established field experiment was used to set up a pot experiment, to evaluate N2O, CH4 and CO2 fluxes from cattle‐slurry‐digestate amended soils. The soil had been treated with farmyard manure, green manure or synthetic N‐fertilizer, 18 months before the pot experiment was set up. Following homogenization and a preincubation stage, digestate was added at a concentration of 250 kg total N/ha eq. Soil GHG fluxes were then sampled over a 64 day period. The digestate stimulated emissions of the three GHGs compared to controls. The legacy of previous soil management was found to be a key determinant of CO2 and N2O flux while edaphic variables did not have a significant effect across the range of variables included in this experiment. Conversely, edaphic variables, in particular texture, were the main determinant of CH4 flux from soil following digestate application. Results demonstrate that edaphic factors and current soil management regime alone are not effective predictors of soil GHG flux response following digestate application. Knowledge of the site management in terms of organic amendments is required to make robust predictions of the likely soil GHG flux response following digestate application to soil. [ABSTRACT FROM AUTHOR]

Summary: Plasma membrane intrinsic proteins (PIPs) are known to be major facilitators of the movement of a number of substrates across cell membranes. From a drought‐resistant cultivar of Oryza sativa (rice), we isolated an OsPIP1;3 gene single‐nucleotide polymorphism (SNP) that is mostly expressed in rice roots and is strongly responsive to drought stress. Immunocytochemistry showed that OsPIP1;3 majorly accumulated on the proximal end of the endodermis and the cell surface around the xylem. Expression of GFP‐OsPIP1;3 alone in Xenopus oocytes or rice protoplasts showed OsPIP1;3 mislocalization in the endoplasmic reticulum (ER)‐like neighborhood, whereas co‐expression of OsPIP2;2 recruited OsPIP1;3 to the plasma membrane and led to a significant enhancement of water permeability in oocytes. Moreover, reconstitution of 10×His‐OsPIP1;3 in liposomes demonstrated water channel activity, as revealed by stopped‐flow light scattering. Intriguingly, by patch‐clamp technique, we detected significant NO3− conductance of OsPIP1;3 in mammalian cells. To investigate the physiological functions of OsPIP1;3, we ectopically expressed the OsPIP1;3 gene in Nicotiana benthamiana (tobacco). The transgenic tobacco plants exhibited higher photosynthesis rates, root hydraulic conductivity (Lpr) and water‐use efficiency, resulting in a greater biomass and a higher resistance to water deficit than the wild‐type did. Further experiments suggested that heterologous expression of OsPIP1;3 in cyanobacterium altered bacterial growth under different conditions of CO2 gas supply. Overall, besides shedding light on the multiple functions played by OsPIP1;3, this work provides insights into the translational value of plant AQPs. Significance Statement: We detected water, CO2 and nitrate transport abilities of rice OsPIP1;3 using different technical approaches. Ectopic expression of the OsPIP1;3 gene in tobacco substantially enhanced plant growth and resistance to water deficit by increasing the photosynthesis rate and root hydraulic conductivity in transgenic plants. This study provides important clues for uncovering the multiple functions played by plant PIP proteins and the related translational value. [ABSTRACT FROM AUTHOR]

Phytoplankton are the unicellular photosynthetic microbes that form the base of aquatic ecosystems, and their responses to global change will impact everything from food web dynamics to global nutrient cycles. Some taxa respond to environmental change by increasing population growth rates in the short‐term and are projected to increase in frequency over decades. To gain insight into how these projected 'climate change winners' evolve, we grew populations of microalgae in ameliorated environments for several hundred generations. Most populations evolved to allocate a smaller proportion of carbon to growth while increasing their ability to tolerate and metabolise reactive oxygen species (ROS). This trade‐off drives the evolution of traits that underlie the ecological and biogeochemical roles of phytoplankton. This offers evolutionary and a metabolic frameworks for understanding trait evolution in projected 'climate change winners' and suggests that short‐term population booms have the potential to be dampened or reversed when environmental amelioration persists. [ABSTRACT FROM AUTHOR]

The El Niño–Southern Oscillation (ENSO) drives variations in terrestrial carbon fluxes by affecting the terrestrial ecosystem via atmospheric teleconnections and thus plays an important role in interannual variability of the global carbon cycle. However, we lack such knowledge on decadal time scales, that is, how the carbon cycle can be affected by decadal variations of ENSO characteristics. Here we examine how, and by how much, decadal ENSO variability affects decadal variability of the global carbon cycle by analyzing a 1,801‐year preindustrial control simulation. We identify two different aspects, together explaining ~36% of the decadal variations in the global carbon cycle. First, climate variations induced by decadal ENSO‐like variability regulate terrestrial carbon flux and hence atmospheric CO2 on decadal time scales. Second, decadal changes in the asymmetrical response of the terrestrial ecosystem, resulting from decadal modulation of ENSO amplitude and asymmetry, rectify the background mean state, thereby generating decadal variability of land carbon fluxes. Plain Language Summary: The El Niño–Southern Oscillation (ENSO) is an important driver of year‐to‐year variation of the global carbon cycle due to its impacts on the global climate variability. For example, most parts of the tropical land experience drought during El Niño events, and therefore rainforests and savanna regions do not capture well carbon dioxide compared to normal years because a high temperature and a lack of precipitation during El Niño events lead to less photosynthesis over the tropics. This is a well‐known feature in year‐to‐year variation, but not in decadal time scales due to a lack of long‐term observations. Here we examine how, and by how much, decadal ENSO variability affects decadal variation in the global carbon cycle by analyzing a 1,801‐year Earth System simulation. We found that two different aspects of decadal ENSO variability, associated with decadal changes in the tropical Pacific Ocean and asymmetric characteristics between El Niño and La Niña, drive decadal change in the terrestrial carbon fluxes. As a result, these two aspects together can explain ~36% of the decadal variability in the global carbon cycle. Key Points: About 36% of decadal variations in global NBP can be explained by two aspects of decadal ENSO variabilityFirst, decadal ENSO‐like variability induces interdecadal changes in terrestrial carbon fluxes via atmospheric teleconnectionsSecond, decadal ENSO modulations in amplitude and asymmetry lead to decadal NBP variability by changing ENSO‐induced residual NBP [ABSTRACT FROM AUTHOR]

Ecosystem function (particularly CO2 fluxes and the subsequent atmospheric transport), synoptic‐scale weather (e.g., midlatitude cyclones), and interactions between ecosystems and the atmosphere can be investigated using a weather‐biosphere‐online‐coupled model. The Vegetation Photosynthesis and Respiration Model (VPRM) was coupled with the Weather Research and Forecasting (WRF) model in 2008 to simulate "weather‐aware" biospheric CO2 fluxes and subsequent transport and dispersion. The ability of the coupled WRF‐VPRM modeling system to simulate the CO2 structures within midlatitude cyclones, however, has not been evaluated due to the lack of data within these weather systems. In this study, VPRM parameters previously calibrated off‐line using eddy covariance tower data over North America are implemented into WRF‐VPRM. The updated WRF‐VPRM is then used to simulate spatiotemporal variations of CO2 over the contiguous United States at a horizontal grid spacing of 12 km for 2016 using an optimized downscaling configuration. The downscaled fields are evaluated using remotely sensed data from the Orbiting Carbon Observatory‐2, Total Carbon Column Observing Network, and in situ aircraft measurements from Atmospheric Carbon and Transport‐America missions. Evaluations show that WRF‐VPRM captures the monthly variation of column‐averaged CO2 concentrations (XCO2) and episodic variations associated with frontal passages. The downscaling also successfully captures the horizontal CO2 gradients across fronts and vertical CO2 contrast between the boundary layer and the free troposphere. WRF‐VPRM modeling results indicate that from May to September, biogenic fluxes dominate variability in XCO2 over most of the contiguous United States, except over a few metropolitan areas such as Los Angeles. Plain Language Summary: Global warming due to increase in greenhouse gases, particularly CO2, is well known as a critical issue facing humanity. CO2 concentration increased quickly over the past two centuries, with the overall trend largely due to fossil fuel emissions. Year‐to‐year variations in CO2 growth rate are not well understood, which is partially due to uncertainty in terrestrial CO2 fluxes. Accurate estimation of terrestrial CO2 fluxes is limited by land cover and land use changes, drought, and weather influences. These factors/processes and their impact on CO2 fluxes and atmospheric mole fractions can be investigated using a weather‐biosphere‐online‐coupled model. The Vegetation Photosynthesis and Respiration Model (VPRM) coupled with the Weather Research and Forecasting (WRF) model (referred to as WRF‐VPRM) is one such tool. In this study, optimal VPRM parameters are implemented into WRF‐VPRM. The updated WRF‐VPRM is then used to simulate CO2 mole fractions over the United States for 2016. The simulation is evaluated using aircraft measurements and remote sensing data. Evaluations show that WRF‐VPRM captures the temporal variation of CO2 concentrations, as well as the horizontal CO2 gradients across fronts and vertical CO2 contrast in the low troposphere. Simulations using this modeling system can be used to help understand regional to global CO2 budgets. Key Points: The simulation is evaluated using CONUS‐scale, long‐term data, and in situ measurements that resolve the structures of midlatitude cyclonesWRF‐VPRM is shown to reproduce the structures in CO2 mole fractions observed within midlatitude cyclonesFrom May to September, biogenic fluxes dominate variability in XCO2 over most of the CONUS except around a few metropolitan areas such as LA [ABSTRACT FROM AUTHOR]

Two cavity ring‐down spectrometers were employed to accurately measure line intensities in a series of near‐infrared carbon dioxide bands including (30012) ← (00001), (30013) ← (00001), and (30014) ← (00001) near 1.6 μm. Relative combined standard uncertainties for these band intensities were less than 0.1% and showed significant, percent‐level deviations with respect to many existing spectroscopic databases (although close agreement was observed with the HITRAN 2016 database in the (30013) ← (00001) and (30014) ← (00001) bands). Further, the resulting line intensities were utilized in Total Carbon Column Observing Network retrievals and led to significantly reduced biases in the (30012) ← (00001) and (30013) ← (00001) bands. These results indicate that refinements of spectroscopic databases are required to meet the accuracy targets of both ground‐ and satellite‐based remote sensing missions. Key Points: Near‐infrared CO2 line intensities measured with combined standard uncertainties below 0.1%Deviations in excess of 1% were found between these measurements and existing databasesThese new intensities led to reduced biases in atmospheric retrievals of CO2 mixing ratios when using two near‐infrared bands [ABSTRACT FROM AUTHOR]

The Southern Annular Mode (SAM) is the dominant mode of climate variability in the Southern Ocean, but only a few observational studies have linked variability in SAM to changes in ocean circulation. Atmospheric potential oxygen (APO) combines atmospheric O2/N2 and CO2 data to mask the influence of terrestrial exchanges, yielding a tracer that is sensitive mainly to ocean circulation and biogeochemistry. We show that observed wintertime anomalies of APO are significantly correlated to SAM in 25‐ to 30‐year time series at three Southern Hemisphere sites, while CO2 anomalies are also weakly correlated. We find additional correlations between SAM and O2 air‐sea fluxes in austral winter inferred from both an atmospheric inversion of observed APO and a forced ocean biogeochemistry model simulation. The model results indicate that the correlation with SAM is mechanistically linked to stronger wind speeds and upwelling, which brings oxygen‐depleted deep waters to the surface. Plain Language Summary: The Southern Annular Mode (SAM) is characterized by variability in the strength of the westerly winds that encircle Antarctica. A more positive SAM index is associated with stronger westerly winds over the ocean at about 60°S latitude. Previous studies based mostly on model simulations have suggested that a positive SAM index is also associated with enhanced upwelling of carbon‐rich waters in the Southern Ocean, which influences the uptake and/or release of carbon dioxide to the atmosphere. The same deep waters that have high carbon also have low concentrations of dissolved oxygen, which can cause subtle variations in atmospheric oxygen levels measured at surface stations. We present an analysis of data sets from three Southern Hemisphere stations where air samples have been collected for 25–30 years. We find that during the Southern Hemisphere winter, anomalies in the atmospheric oxygen record are correlated to the SAM index; we find weaker correlations between anomalies in atmospheric carbon dioxide and the SAM index. These results are consistent with variability in air‐sea oxygen fluxes from a model simulation. The model results indicate that the observed relationship between SAM and air‐sea oxygen fluxes is due to both stronger wind speeds and increased upwelling of oxygen‐depleted deep waters. Key Points: Significant correlations are found between winter atmospheric potential oxygen and the Southern Annular Mode at three long‐term observing sitesA similar relationship between winter air‐sea O2 flux and SAM is found in APO inversion products and a hindcast ocean model simulationOcean model simulations indicate that negative winter APO anomalies are linked to stronger wind speeds and ventilation of O2‐depleted deep water [ABSTRACT FROM AUTHOR]

Understanding what physically sets the shape of temperature distributions will enable more robust predictions of local temperature with global warming. We derive the relationship between the temperature distribution shape and the advection of temperature conditionally averaged at each temperature percentile. This enables quantification of the shift of each percentile that is due to changes in the mean temperature, in horizontal temperature advection, and other processes (e.g., radiation and convection). We use this relationship to examine global model simulations in an idealized aquaplanet model with increasing carbon dioxide. Changes in the distribution with doubling and quadrupling of carbon dioxide are significant, and they are caused by different processes. We find that midlatitude temperature distributions can be explained mostly by the horizontal advection, except in the upper and lower 10% of the distribution. Key Points: Distributions of temperature for an aquaplanet model are explained in terms of horizontal advection of temperature and other processesThe shape of midlatitude distributions can be explained by horizontal advection, except in the upper and lower 10% of the distributionAt each percentile, we decompose changes to the distributions into changes in the mean, in horizontal advection, and in other processes [ABSTRACT FROM AUTHOR]

Friction and wear remain the primary modes for energy dissipation in moving mechanical components. Superlubricity is highly desirable for energy saving and environmental benefits. Macroscale superlubricity was previously performed under special environments or on curved nanoscale surfaces. Nevertheless, macroscale superlubricity has not yet been demonstrated under ambient conditions on macroscale surfaces, except in humid air produced by purging water vapor into a tribometer chamber. In this study, a tribological system is fabricated using a graphene‐coated plate (GCP), graphene‐coated microsphere (GCS), and graphene‐coated ball (GCB). The friction coefficient of 0.006 is achieved in air under 35 mN at a sliding speed of 0.2 mm s−1 for 1200 s in the developed GCB/GCS/GCP system. To the best of the knowledge, for the first time, macroscale superlubricity on macroscale surfaces under ambient conditions is reported. The mechanism of macroscale superlubricity is due to the combination of exfoliated graphene flakes and the swinging and sliding of the GCS, which is demonstrated by the experimental measurements, ab initio, and molecular dynamics simulations. These findings help to bridge macroscale superlubricity to real world applications, potentially dramatically contributing to energy savings and reducing the emission of carbon dioxide to the environment. [ABSTRACT FROM AUTHOR]

Summary: Stomata are cellular breathing pores on leaves that open and close to absorb photosynthetic carbon dioxide and to restrict water loss through transpiration, respectively. Grasses (Poaceae) form morphologically innovative stomata, which consist of two dumbbell‐shaped guard cells flanked by two lateral subsidiary cells (SCs). This 'graminoid' morphology is associated with faster stomatal movements leading to more water‐efficient gas exchange in changing environments. Here, we offer a genetic and mechanistic perspective on the unique graminoid form of grass stomata and the developmental innovations during stomatal cell lineage initiation, recruitment of SCs and stomatal morphogenesis. Furthermore, the functional consequences of the four‐celled, graminoid stomatal morphology are summarized. We compile the identified players relevant for stomatal opening and closing in grasses, and discuss possible mechanisms leading to cell‐type‐specific regulation of osmotic potential and turgor. In conclusion, we propose that the investigation of functionally superior grass stomata might reveal routes to improve water‐stress resilience of agriculturally relevant plants in a changing climate. Significance Statement: A key challenge for plants is to efficiently use water, particularly when growing in a hot and dry climate. Stomata – cellular breathing pores on leaves that mediate gas exchange between plant and atmosphere – have a pivotal role in controlling water‐use efficiency. Stomata can adjust their pore size to balance carbon dioxide uptake with water vapour loss. Interestingly, grasses like the three most important food crops rice, maize and wheat have improved stomata that can regulate water use more efficiently by opening and closing faster than other plants. Rapid stomatal movements are linked to the grass stomata's unique morphology consisting of dumbbell‐shaped guard cells and lateral subsidiary or helper cells. Recently, work on domesticated and wild grass species has started to reveal some of the secrets regarding how grass stomata form and function more efficiently. [ABSTRACT FROM AUTHOR]

Summary: The intricate and interconnecting reactions of C3 photosynthesis are often limited by one of two fundamental processes: the conversion of solar energy into chemical energy, or the diffusion of CO2 from the atmosphere through the stomata, and ultimately into the chloroplast. In this review, we explore how the contributions of stomatal morphology and distribution can affect photosynthesis, through changes in gaseous exchange. The factors driving this relationship are considered, and recent results from studies investigating the effects of stomatal shape, size, density and patterning on photosynthesis are discussed. We suggest that the interplay between stomatal gaseous exchange and photosynthesis is complex, and that a disconnect often exists between the rates of CO2 diffusion and photosynthetic carbon fixation. The mechanisms that allow for substantial reductions in maximum stomatal conductance without affecting photosynthesis are highly dependent on environmental factors, such as light intensity, and could be exploited to improve crop performance. Significance Statement: Plant photosynthesis relies on diffusion of CO2 from the atmosphere to the chloroplasts through the stomatal pores. The distribution and morphological characteristics of stomata influence this and are of particular importance when attempting to understand or improve on rates of carbon fixation. Nonetheless, alterations expected to affect stomatal conductance do not always cause corresponding alterations in photosynthetic carbon assimilation. This review explores the factors that are likely to cause this observed disconnect between maximum stomatal conductance and photosynthesis. [ABSTRACT FROM AUTHOR]

The plume composition at Enceladus contains clues about conditions and processes in the interior. We present new geochemical interpretations of Cassini mass spectrometry data from the plume gas and salt‐rich ice grains. It is found that self‐consistency between the data sets can be achieved with a derived range of 10−4.6 to 10−3.2 for the activity of CO2 in Enceladus' ocean. This range is compatible with long‐term buffering by reduced or oxidized seafloor rocks containing quartz, talc, and carbonate minerals in the MgO–FeO–SiO2–CO2–H2O system. Reaction path modeling shows that these types of rocks can be produced from accreted CO2‐rich fluids reacting with hydrous chondritic rocks over an intermediate regime of carbonation. These results, together with previous findings of silica and H2 at Enceladus, support the hypothesis of a heterogeneous structure for the rocky core (carbonated upper layer, serpentinized interior), which provides a geochemical gradient for habitability. Plain Language Summary: Enceladus, an ocean‐harboring moon of Saturn, erupts a plume that contains gases and frozen sea spray into space. By understanding the composition of the plume, we can learn about what the ocean is like, how it got to be this way, and whether it provides environments where life as we know it could survive. This study presents a new perspective for analyzing the plume composition to estimate the concentration of dissolved carbon dioxide in the ocean. We find that the derived range based on two different data sets is intriguingly similar to what would be expected from the dissolution and formation of certain mixtures of silicon‐ and carbon‐bearing minerals at the seafloor. The deduced combination of minerals may be indicative of a fundamental process that has sequestered a large amount of Enceladus' initial inventory of carbon dioxide into the rocky core. This inference echoes an emerging vision of a complex interior that hosts geochemically diverse environments. The dynamic interface of such complexity is where energy sources for possible life may arise. Key Points: New estimates of the thermodynamic activity of CO2 in Enceladus' ocean based on the carbonate chemistry of the plumeFormation of CO2‐buffering assemblages of quartz‐talc‐carbonate from partial carbonation of chondritic compositionsDistinct sources of observed CO2, silica, and H2 imply mineralogically and thermally diverse environments in the rocky core [ABSTRACT FROM AUTHOR]

Summary: Plants grow and transpire during the night. The aim of the present work was to assess the relative flows of carbon, water and solutes, and the energy involved, in sustaining night‐time transpiration and leaf expansive growth under control and salt‐stress conditions.Published and unpublished data were used, for barley plants grown in presence of 0.5–1 mM NaCl (control) and 100 mM NaCl.Night‐time leaf growth presents a more efficient use of taken‐up water compared with day‐time growth. This efficiency increases several‐fold with salt stress. Night‐time transpiration cannot be supported entirely through osmotically driven uptake of water through roots under salt stress. Using a simple three‐ (root medium/cytosol/vacuole) compartment approach, the energy required to support cell expansion during the night is in the lower percentage region (0.03–5.5%) of the energy available through respiration, under both, control and salt‐stress conditions. Use of organic (e.g. hexose equivalents) rather than inorganic (e.g. Na+, Cl−, K+) solutes for generation of osmotic pressure in growing cells, increases the energy demand by orders of magnitude, yet requires only a small portion of carbon assimilated during the day.Night‐time transpiration and leaf expansive growth should be considered as a potential acclimation mechanism to salinity. See also the Commentary on this article by Sanders, 225: 1047–1048. [ABSTRACT FROM AUTHOR]

New Finding: What is the central question of this study?Transition to supine posture induces an inspiratory load associated with cortical activation in awake healthy subjects. Some obstructive sleep apnoea patients exhibit this cortical activity in the sitting position contributing to the arousal‐dependent compensation of their upper airway abnormalities. Does a transition to the supine posture in awake obstructive sleep apnoea patients increase this cortical activity?What is the main finding and its importance?The transition to supine posture induces a reduction in the cortical activity despite evidence of an increase in genioglossus activity, suggesting that genioglossus activation is not driven by cortical activity. The anatomy and mechanical properties of the upper airway (UA) depend on posture. Lying in a supine position causes cephalad fluid shift to the neck, thus narrowing the UA and predisposing the individual to obstructive sleep apnoea (OSA). Increased UA dilator muscle activity during wakefulness prevents the UA collapse but the underlying mechanism has not yet been elucidated. In the sitting position during wakefulness, some OSA patients exhibit preinspiratory cortical activity (preinspiratory potential, PIP) probably related to UA abnormalities. The aim of this study was to investigate changes in the preinspiratory cortical activity and UA dilator muscle in OSA patients during postural challenge. An electroencephalogram was used to detect PIP, and the genioglossus electromyographic activity and ventilation were analysed in 17 awake, male OSA patients while they were sitting, just after lying down, and then in response to leg positive pressure to enhance cephalad fluid shift. The prevalence of PIP decreased from 53% (sitting) to 12% (supine) (P = 0.002) in association with increased genioglossus activity (tonic from median (25th, 75th centiles) 2.3 (1.8, 2.8)% to 3.6 (1.7, 5.0)% of voluntary deglutition, P = 0.019; phasic from 2.3 (1.9, 2.8)% to 3.7 (2.0, 6.1)%, P = 0.024), and with increased transcutaneous carbon dioxide pressure (from 43.0 (42.4, 44.2) to 44.6 (43.5, 45.2) mmHg). No change was observed during leg‐positive‐pressure application. Moving from the sitting position to the supine position reduces respiratory‐related premotor cortical activity in awake OSA patients. The concomitant increase in genioglossus activity, therefore, is not driven by cortical respiratory activity. [ABSTRACT FROM AUTHOR]